Mesenchymal stromal cells (MSCs) are considered an important tool in tissue engineering due to their multilineage potential in vitro as in vivo beyond their capacity to produce bioactive molecules involved in tissue regeneration. MSCs are essential elements of the microenvironment because they are the precursors of all stromal cells. MSCs influence HPC functions, such as proliferation, apoptosis, and clonogenic growth, directly via cell-cell contacts or indirectly via the secretion of soluble factors. This book reviews the biology, mechanisms of action and clinical uses of MSCs. Chapter One analyzes the modulation of adhesion molecules on MSCs to help in understanding their possible contribution to cancer initiation and progression. Chapter Two studies adipose derived MSCs in cancer therapy. Chapter Three discusses the improvement of clinical uses of MSCs by 3D scaffold-free constructs. Chapter Four reviews the application of MSCs in veterinary medicine.